Method of producing rubber articles



Dec. 16, 1930. 'L 1,785,083

METHOD OF PRODUCING RUBBER ARTICLES Filed Oct. 17, 1928 Invenior: Hum 12. fiaew'i'ei;

I y ywg ww Patented Dec. 16, 1930 UNITED STATES PATENT OFFICE HANS RICHARD HAERTEL, OF WRENTHAM, MASSACHUSETTS, ASSIGNOR TO THOMAS H.

' BUMPER, TRUSTEE. OF NEWTON, MASSACHUSETTS I METHOD OF PRODUCING RUBBER ARTICLES Application filed October 17, 1928. Serial No.- 313,032.

This application is a continuation in part of my application SerialNo. 231,540, filed November 7, 1927.

My invention relates'to rubber coated articles, as for example'rubberized sheets for making raincoat material, and to apparatus for and processes of making the same.

The invention will be best understood from the following description of an example of an article made according to the invention, and description of one manner of carrying out the improved process and of one exam 1e of apparatus for use in performing t is process. a

The drawing shows diagrammatically a calendering machine and auxiliary apparatus for forming rubber-coatedtextile sheets.

Referring to the drawing, a sheet 1 of textile material may be fed from a roll 2 and passed between the lower roll 3 and intermediate roll 4 of a calendering machine. A

mass of suitably colored and prepared rubber 5 may be placed on a shel 6 and fed to pass between the upper roll 7 and intermediate roll 4 to form a thin layer of rubber 8 which adheres to the surface of the intermediate roll and passes between the latter and the lower roll with the textile sheet,

whereby the layer 8 of rubber is caused to adhere to the latter.

Conveniently the calendering rolls may be heated to facilitate the above described operation, such heat aided by the squeezing ac tion of the rolls on the rubber causing-the latter to become sticky. It has been found that the stickiness of the rubber continues to exist 'evenafter the rubber has become cold, which stickiness if not eliminated will prevent convenient handling of the product during subsequent operations thereon.

According to prior practice, the surface of the rubber, after the sheet leaves the rolls of the calendering machine, is dusted or brushed with finely powdered clay or like materlal to destroy the superficial stickiness and thus permit the material readily to be handled during the subsequent operatlon of adding thicknesses of rubber by again passing the sheet through the rolls' of a calendering machine, after which it is again dusted with the comes distributed by drafts. throughout the various rooms and buildings constitutin the plant, causing the various rubber products if manufactured to become specked with the same; The result of dust, therefore, is seriously to impair both the quality of the-various products and the efiiciency of the operators.

The present invention among other things has for its object the elimination of the dust nuisance while securing an improved product. To this end, therefore, the invention contemplates destroying the superficial stickiness of the rubber by applying thereto a substance handled in the form of a liquid, and for this purpose, in the submitted embodiment of the invention, the rubber-coated sheet after it passes from between the rolls of the calendering machine is guided over rolls 9 and ,10 to a tank 11 containing a liquid coating substance, the level of which liquid is indicated at 12.

Above the tank 11 is pivoted a roller 13 which extends at its lower portion to beneath the level of the liquid contained in the tank. The sheet is guided over the tank by the roller 10 and a second roller 14, with the surface of the rubber in contact with the roller 13 and the upper edge 15 of the tank. The roller 13 being revolved by the sheet passing over it, causes the surface of the rubber to be wet with the liquid, while the edge 11 of the tank scrapes off the excess liquid, causing a film of liquid of substantially uniform thickness to be distributed over the surface of the rubber without wetting the textile backing of the sheet. The sheet is now passed over the rollers 15 and 16 and rolled as at 17 on an arbor 18. v

During the passage of the sheet from the tank to the roll 17, the liquid deposited upon the rubber will dry, which drying is facilitated by the fact that the rubber is warm at the time the liquid is applied and by causing the draft from a fan 19 to be projected against the surface of the rubber during the passage of the sheet from the roller 15 to the roller 16.

As an example of the material used for coating the rubber, but without limitation thereto, the tank 11 may contain an ammonia (NILOH) solution of magnesium carbonate, with some alcohol, if desired, to facilitate drying. I have found that this solution will dry rapidly and completely, leaving an adhering residue which will not absorb moisture, and which is inert with respect to the rubber compound so as not deleteriously to affect its physical or chemical properties. Weak solutions, say about 1 pound of magnesium carbonate dissolved in 4 gallons of 26 Baum ammonia water, will leave an entirely invisible coating, while stronger solutions, say about 2 pounds of magnesium carbonate dissolved in 4 gallons of 26 Baum ammonia water, will result in a smooth, slightly grayish or white coating. In each instance the coating is invisible when varnish, as for example alcohol or water shellac, or other varnish commonly employed in the art, ifs subsequently applied to the rubber surace.

The probable action which occurs in the process of forming the mineral coating is that, because metal ammonium carbonates are unstable, particularly when warm, both the ammonia (NIL) and water contents of the solution pass off in gas or vapor form, leaving a residue composed of minute, individually transparent crystals of the metal carbonate, which coating therefore is invisible without the surface being varnished when weak solutions are employed, and invisible with a subsequently varnished surface when strong solutions are employed. Usually, but not necessarily, the surface of the final rubber layer, after the mineral coating is applied thereto, is varnished subsequent to curing the sheeting, varnish, it being understood, giving a high gloss finish, the degree of gloss of which may be regulated by use of more or less dull varnish. By use of the improved coating applied according to the invention the streaked appearance of the finished varnished surface, resulting by use of prior methods, is entirely avoided.

As substitutes for magnesium carbonate I may employe other metal carbonates, as for example zinc carbonate, lead carbonate, and silver carbonate, which are soluble in ammonia and inert with respect to rubber (see Hand Book of Chemistry and Physics by Hogman, Coolbaugh & Senseman, published by The Chemical Rubber Company, Cleveland, Ohio, 1918). Those metal carbonates soluble in ammonia, such as copper-carbonate, which deleteriously attack rubber or the constituents of the rubber compound, it will be understood by those skilled in the art will give inferior results.

-According to another prior method of treating rubber surfaces to remove the sticki-' ness thereof, the surface has been treated with bromine water or solutions of bromine salts. It has been found that, although this prior method to a certain extent secures a product of satisfactory appearance, it does so only at a sacrifice of quality of the product, for bromine or the like reacts with the rubber to form a chemical combination comprising bromine and oxygen, and therefore acts to eliminate the stickiness of the rubber by destroying said surface in respect to its being rubber. This initial oxidizing of the surface by the bromine results in time in deeper penetration of the oxidized layer with resulting shorter life of the product. Also it has been proposed to eliminate tackiness of rubber surfaces by dusting these surfaces with metal salts of fatty acids and of aromatic or hydroaromatic acids which are absorbed into the rubber during vulcanization. These salts of organic acids have the defect of attacking the rubber with resulting destruction of its elasticity. and cause blooming and other surface blemishes, the stearic acid salts particularly giving the surface a greasy appearance. The improved method is distinguished from these prior methods in that the coating material used, as for example the magnesium salt mentioned above, is chemically inert with respect to rubber, and therefore causes no initial destruction of the surface of the rubber, while at the same time it improves instead of detracts from its finish. It therefore will be observed that in its specific aspect my invention, besides eliminating the dust nuisance and securing a product of satisfactory appearance, contemplates the employment of a coating substance which is in ert with respect to rubber and which will permit the superposing of additional layers of rubber and will be transparent or colorless when the surface is varnished.

The treatment of the rubber surface by dusting with clay and organic salts and treatment with bromine also acts to dull the surface of the rubber, and where the product is brightly colored, as is commonly the case, additional pigment is required in the rubber compound to overcome this dulling effect. Therefore, as this dulling of the rubber surface, when desired, can be avoided in the practice of the present invention, a material saving in expensive coloring material may be effected.

Further I have found that, where the product consists of two or more superimposed rubber layers,-treatment of the rubber surfaces according to the present invention results in sufficient adherence between the layers and such elimination of tackiness in the upper surface of the final layer asto enable the material to be embossed, prior to curing, in an embossing press, without separation of thelayers, as heretofore has been tlle case with a product made by prior metho s.

It will be understood that the above described article, apparatus, and method are illustrative only, and that wide deviations may be made within the scope of the invention without departing from its spirit.

Claims:

1. That improvement in the method of producing rubberized textile sheets which comprises applying'a layer of rubber to a textile sheet and removing the tackiness of the rubber by wetting the exposed surface thereof with a film of ammonia solution of a metal carbonate.

2. That improvement in the method of producing rubberized textile sheets which comprises applying a layer of rubber to a textile sheet and removing the tackiness of the rubber by Wetting the exposed surface thereof with a film of ammonia solution of magnesium carbonate.

3. That improvement in the method of producing rubberized textile sheets which comprises applying a layer of rubber to a textile sheet and removing the tackiness of the rubber by wetting the exposed surface thereof with a film of ammonia solution of a metal carbonate, and after drying of the surface coating it with shellac.

4. That improvement in the method of producing rubberized textile sheets which exposed surface thereof. with a film of ammonia solution of a metal carbonate.

6. That improvement in the method of producing rubberized textile sheets which comprises surfacing said sheets with rubber compound by use of hot calender rolls, and while the rubber is warm and tacky wetting the exposed surface thereof with a film of ammonia solution of magnesium carbonate.

7. An article of manufacture comprising a rubber coated textile sheet, the exposed surface of the rubber having thereon a substantially invisible and transparent coating of metal carbonate particles covered by a HANS RICHARD HAERTEL. 

